Are you annoyed by having too much systems to take care of? You just want to watch TV using your Plex / Fritzbox cable setup?
Try this experimental server instead of using the TVHeadend / TVHProxy combination.
Cudos to TVHProxy folks, as this is heavily inspired by them.
This is a simple Sinatra server that just needs ruby and ffmpeg as prerequisites. Please check the Dockerfile for further explanation on how to handle. Has been tested on my synology.